Heater for fuel injection system



June 3, 1958 J. DOLZA HEATER FOR FUEL INJECTION SYSTEM 5 Sheets-Sheet 1 Filed May 6, 1957 INVENTO cfahz @[za ATTORNEY June 3, 1958 r J. DOLZA 2,337,073

HEATER FOR FUEL INJECTION SYSTEM Filed May 6, 1957 s Sheets-Sheet 2 Ill ll/Illll 1 ill I iiNWWWN! i\\\\\\\\\\\\\\\\\\\ I'I'IIIIIIIIA INVE NTb R r/a/z Zb/ze ATTORNEY June 3, 1958 J; DQ'LZA HEATER FOR FUEL INJECTION SYSTEM 3 Sheets-Sht :5

Filed May a, 1957 ATOREY United States Patent HEATER FOR FUEL INJECTION SYSTEM John Dolza, Fenton, Micl1., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application May 6, 1957, Serial No. 657,180

15 Claims. (Cl. 123-122) The present device relates to a heater for a fuel injection system and more particularly for use on such system utilizing an atmospheric type nozzle. An atmospheric nozzle of the type shown and described in copending application Serial No. 512,175 Homfeld et al., filed May 31, 1955, utilizes a plurality of small openings or orifices which under certain ambient atmospheric conditions tend to ice up and upset the fuel air ratio.

This invention relates to a device whereby heated air is supplied to the atmospheric nozzles during conditions when such icing is likely to take place. In this device the atmospheric air which has heretofore been supplied directly to the nozzle from a point anteriorly of the air induction venturi is instead caused to flow through a heated section of the engine until such time'as the overall engine temperature reaches a value which will insure ice free operation of the nozzles.

The present invention utilizes a temperature responsive air valve which is mounted within the engine exhaust manifold and which draws air from the induction passage and causes the latter to flow through a heated portion of the exhaust manifold enroute to the atmospheric nozzle. The device is constructed so as to cause such atmospheric nozzle air to be progressively bypassed around the heater device as engine temperature increases.

When used with a fuel injection system embodying a signal modifier valve of the type shown and described in copending application Serial'No. 658,091, Dolza et al., filed May 9, 1957, the present heater mechanism is also adapted to control the actuation of the signal modifier valve. In this way a single thermostatic or temperature responsive mechanism may be utilized to actuate the plurality of temperature dependent devices.

A detailed description of the present invention as well as other objects and advantages are set forth in the detailed description which follows.

In the drawings:

Figure l is a partially sectioned elevational. view of a fuel injection system embodying the subject invention;

Figure 2 is an enlarged sectional View of the subject heating mechanism;

Figure 3 is a view along line 3-3 of Figure 2;

Figure 4 is a view along line 4-4 of Figure 2;

Figure 5 is a view along line 5-5 of Figure 2;

Figure 6 is a view of the heater mechanism when t.e engine has warmed;

Figure 7 is a view along line 7-7 of Figure 6; Figure 8 is a view along line 83 of Figure 6; Figure 9 is a view along line 9-9 of Figure 6; Figures 10 and 11 are detailed views of the heater mechanism lock-out device; and

Figure 12 is a. fragmentary view of the atmospheric nozzle.

The fuel injection system, per se, functions in the same manner as'tliat shown and described in copending application Serial No. 608,853 Dolza, filed September 10, 13-956,- and will be described in the present case only insofar as is necessary to provide the proper environment for the subject invention.

An internal combustion engine is shown generally at 10 and includes a cylinder block 12 and heads 14 and 16. An air induction casing 13 is mounted on and communicates with an air manifold or plenum chamber 20 from which a plurality of individual cylinder intake passages 22 communicate with the cylinder heads 14 and 16. A fuel inlet conduit 24 communicates with each intake passage 22 and terminates in an atmospheric nozzle of the general type described in the aforenoted Homfeld application.

A throttle valve 26 is disposed in the air induction passage 27 posteriorly of the venturi 28. In the system with which the present invention has been illustrated, a signal modifier valve 30 is also disposed in the air induction passage anteriorly of the venturi.

In previous fuel injection systems utilizing atmospheric nozzles the air has been supplied to the nozzle through a conduit which communicated with the induction passage anteriorly of the venturi. As a result of introducing air to the nozzle from this point during certain atmospheric conditions, e. g. high relative humidity and ambient temperatures below 40, icing has frequently occurred in the reference holes of the nozzle. Icing at this point disturbs the fuel-air ratio by preventing atmospheric venting which is the prime purpose of utilizing such nozzle as described in the Homfeld application.

Accordingly, in the present device a heater mechanism indicated generally at 32 is provided which causes the atmospheric reference air to flow from the induction passage through the exhaust manifold where it is heated and thence to the atmospheric nozzle where the heated air prevents icing. More specifically, internal combustion engines of the type with which fuel injection systems are utilized include exhaust cross-over passages which with conventional carburetors are utilized to provide a hot spot for the vaporization of fuel. When employing fuel injection systems it has been customary to eliminate the exhaust cross-over passage and block the cross-over ports. In the present instance, the heater mechanism 32 is adapted to be mounted within the exhaust passage 33 to expose the former to engine temperatures which are symptomatic of the need for heated air at the atmospheric nozzles.

The heater device 32 is of a capsule or cartridge type construction and includes an elongated tubular sleeve member 34 closed-at its inner end and communicating at its upper end with an enlarged cylindrical section 36 housing a rotatable valve mechanism 38. The cylindrical section 36 of the heater device 32 is communicated with the induction passage 27 through a conduit 40 and in turn communicates with the atmospheric nozzles through a conduit 42. A rotatable shaft 44 is centrally supported within a sleeve 46 mounted in casing 34. The shaft projects within the tubular casing 34 and terminates near the lower end thereof. A bimetallic coil element 48 is concentrically disposed about the lower end of rotatable shaft 44 and is fixed at one end thereto. The other end Sll of the element 48 is suitably fixed to the tubular casing 34. As thus disposed the thermostatic coil element is mounted within thatportion of the tubular casing 34 which projects within the exhaust passage 33.

The air distributing or diverting valve mechanism 38 is mounted in the cylindrical section 36 of the heater mechanism 32 and includes a-plurality of axially spaced circular plates 52 and 54 fixedly mounted on the shaft supporting sleeve portion 56. The plates 52 and 54 are perforated to permit the flow of air therethrough in accordance with the various positions of a movable part of the valve mechanism 38. As best seen in Figure 2 the upper plate 52 is'axially positioned on the supporting 3 sleeve 56 so as to intersect the air inlet conduit 40 permitting air to flow above and below the plate 52.

The outlet passage 42 is mounted on the casing 36 such that the upper plate 52 terminates thereabove in such a way that the movable part of the valve mechanism is adapted to block the flow of air above the plate to the outlet passage. The lower plate 54 is axially spaced from the upper plate 52 so as to radially intersect casing section 36 to terminate below both the inlet and outlet passages 40 and 42. As seen in Figure 4, air diverters or bafiles 58 and 60 are positioned between plates 52 and 54 so as to prevent air from intake passage 40 flowing directly between the plates 52 and 54 to outlet passage 42. In other words, the air in flowing between passages 4t} and 42 must either be from above the upper plate 52 or from below the lower plate 54. In addition, a similar type bafiie consisting of a pair of plates 62 and 64 is supported within the tubular casing 34 and extendsfrom below the lower plate 54 to thermostatic element 48 so as to divide the tubular casing into chambers 66 and 68. In this way the air which enters the tubular casing 34 must flow downwardly through chamber 66, as shown by the arrows in Figure 2, to the lower end of the casing and around the thermostatic element 48 and upwardly through chamber 68 to outlet passage 42. It will be seen in Figure 2 that the shaft supporting sleeve portion 46 is formed from the plates 62 and 64.

The division of air flow through the heater mechanism 32 is determined by the valve mechanism 38 in accordance with engine temperature as will now be described. Valve mechanism 38 comprises a first sleeve 70 which is disposed in the cylindrical casing section 36 above the upper plate 52. Sleeve 70' has a pair of valve elements 72 and 74 formed at the lower end thereof and which elements are generally of quadrant shape and disposed 180" from each other as best seen in Figure 3. The quadrant shaped valve elements 72 and 74 are adapted to cooperate with similarly formed quadrantal openings 76, 78 and 80 in upper end plate 52 to control the fiow of air from above the plate to the space between the plates 52 and 54. 'A similar quadrant shaped valve element 82 is formed-on a sleeve 84 suitably fixed to sleeve 70 for rotation therewith. Valve element 82, as seen in Figures 5 and 6, is adapted to cooperate with quadrantal opening 86 in lower plate 54 to control the flow of heated air from within tubular casing 34 to the outlet passage 42.

In general the purpose of the valve mechanism 38 is to insure that when the engine is cold the atmospheric nozzle reference air drawn from the induction passage 27 will flow through the communicating passage 40, be diverted to flow within the tubular casing 34 of the heater mechanism 32 where it will be exposed to the exhaust gas heat within the cross-over passage 33, caused to flow to the outlet passage 42 and thence to the atmospheric nozzle 25. As seen in Figure 12, the nozzle includes the reference air passages 29 which communicate through an air chamber 31 with air passage 42.

As seen in Figure 3, the valve element 72 is adapted to block quadrantal opening 76 in upper plate 52 preventing the flow of air from above the plate directly to the outlet passage 42. At the same time companion valve element 74 uncovers the opening 78 permitting the air above the plate 52 to flow downwardly through the space between the plates 52 and 54 where it joins the air directly flowing into the space from the passage 40 flowing through openings 88 and 90 in the lower plate 54 and into tubular casing chamber 66. Under these conditions valve element 82 uncovers plate opening 92 communicating the tubular casing chamber 68 with the space between the plates and permitting the heated air to flow out of outlet casing 42. i

As the temperature in the. exhaust passage 33 increases, the thermostatic element 48 will unwind causing the shaft 44 and sleeves 70 and 84 to be rotated to vary the registry between the valve elements 72, 74 and 82 and the associated quadrantal openings in end plates 52 and 54. Thus as the engine temperature increases and with it the decreased likelihood of atmospheric nozzle icing, the need for supplying heated air to the nozzles also decreases. For reasons of volumetric efficiency it is preferable to supply the cylinders with heatedair no longer than necessary. Accordingly, as the engine temperature increases the valve element 72 is moved to gradually uncover upper end plate opening 76 until the valve elements reach the ultimate position shown in Figure 7. Under these conditions the air above the end plate 52 is adapted to flow directly through the end plate opening 76 into the outlet passage 42. At the same time the valve element 82 is moved to a position shown in Figure 8 in which the air outlet opening 86 in the lower plate 54 is blocked cutting ofi the flow of heated air to the outlet passage 42. Thus it will be seen that with the engine warm the reference air for the atmospheric nozzle 25 flows directly from the communicating passage 40 through the upper end of casing 36 to the outlet passage 42 and in this way bypasses the tubular or heater portion 34 or" the mechanism.

To insure that air is continuously circulated through the tubular casing 34 to prevent damage thereto from overheating, a conduit 96 communicates at one end with the induction passage 27 posteriorly of throttle 26 and at its other end with an opening 98, Figure 4, in the cylindrical casing portion 36 of the heater mechanism. The opening 98 in the'cylindrical casing 36 communicates with chamber 68 of the tubular casing 34 through an opening 100 in plate 54. Opening 100 is uncovered by valve element 82 when theengine is warm insuring a continuous flow of air through casing 34 to cool the thermostatic element 48. A similar opening 102 is pro-,, vided in plate 52 which permits air to flow through conduit 96 from above plate 52 when valve element 74 uncovers the opening. It is apparent that the air flow through the conduit 96 will be occasioned by themanifold depression acting on the induction passage end of the conduit.

As already noted, the fuel injection system with which the present invention has been illustrated utilizes a metering signal modifying valve 30 for coldstart and running enrichment. The function of this element is described in the copending application Serial No. 658,091, Dolza et al. filed May 9, 1957. Suffice it to say with respect to the present invention, the signal modifying valve 30 is also adapted to be controlled by the thermostatic element 48. As already described the shaft 44 is adapted to be rotated by the thermostatic coil element 48. A lever 104 is fixed to the upper end of shaft 44 and has one end of a link 106 articulated thereto. The other end of link 106 is likewise articulated to a lever 108 fixed on the signal modifier valve shaft 110. Thus with the engine cold the thermostatic element 48 is adapted to retain the signal modifier valve in a closed position as shown in Figure 1. As the engine warms the thermostatic element through shaft 44, levers 104 and 108 and link 106 is adapted to gradually open the valve 30.

Inasmuch as the subject heater mechanism is not necessary during warm weather operation, means has been provided whereby the heater mechanism may be rendered inoperative. The shaft 44 is adapted to rotate the sleeves 70 and 84 which have the valve elements 72, 74 and 82 thereon. As best seen in Figure 10, the connection between shaft 44 and sleeves 70 and 84 is achieved through a stud element 112 thread-ablysupported on lever 1'04 and adapted to threadably engage a similar lever 116 formed on the upper end of sleeve 70. When the stud 112 connects the. levers 104 and 116 the rotary movement of shaft 44 is transmitted to sleeves 70 and 84 causing the operation of the valve mechanism as described, supra. When it is desired, as suggested, to disconnect the heater mechanism for warm weather operation stud 112 is withdrawn and the lever 116 rotated to esame the position which blocks the flow of atmospheric nozzle air through the tubular heater casing 34, as described. The lever 116 may be suitably locked in the warm weather position by threading stud 112 therethrough and into engagement with an anchor plate 118 fixedly mounted on casing 36. In this way the heater mechanism is rendered inoperative, at the same time permitting normal operation of the signal modifier valve 30 by thermostatic coil 48.

The communication of passage 96 with the induction passage 27 posteriorly of the venturi 27 is desirable in that it insures that all air flow through the system is past the venturi thereby insuring a maximum metering signal under all flow conditions. A variable restriction 120 is provided in the heater inlet connection 40 to apply a slight depression on the downstream side of the fuel orifices of the nozzles 25. In this way idle and off-idle enrichment may be provided.

I claim:

1. A fuel injection system for an internal combustion engine comprising an air intake passage having a v'enturi formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, intake. passages communicating the induction passage with the individual cylinders of the engine, .a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device for causing said air to flow through a heated portion of said engine to provide heated air flow through said nozzles, and means responsive to engine temperature for causing said air flow to bypass said device as engine temperature increases.

2. A fuel injection system for an internal combustion engine comprising an air intake passage having a ventnri formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, intake passages communicating the induction passage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said inductionvpascage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device to provide heated air flow through said nozzles, and means responsive to engine temperature for bypassing said device as engine temperature increases.

3. A fuel injection system for an internal combustion engine comprising an air intake passage having a venturi formed therein, a throttle valve disposed in said intake passage postericrly of said venturi, intake passages communicating the induction passage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device to provide heated air flow through said nozzles, means responsive to engine temperature'operatively connected to said device for bypassing air flow therearound as engine temperature increases, and means for interrupting the operative connection between said device and said temperature responsive means.

4. A fuel injection system for an internal combustion engine comprising an air intake passage having a venturi formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, a second valve disposed in'said induction passage anteriorly of said venturi, intake pass-ages communicating the induction pas sage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device for causing said air'to flow through a heated portion of said engine to provide heated flow through said nozzles, means responsive to engine temperature for causing said air flow to bypass said device as engine temperature increases, and means interconnecting said temperature responsive means and said second valve whereby said valve will be opened as engine temperature increases.

5. A fuel injection system for an internal combustion engine comprising an air intake passage having aventuri formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, a second valve disv posed in said induction passage anteriorly of said venturi, intake passages communicating the induction passage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device for causing said air to flow through a heated portion of said engine to provide heated air flow through said nozzles, means responsive toengine temperature for causing said air flow to bypass said device as engine temperature increases, means interconnecting said temperature responsive means and said second valve whereby said valve will be opened as engine temperature increases, and means for rendering said air heating device inoperative without affecting the operation of said second valve.

6. A fuel injection system for an internal combustion engine comprising an air intake passage having a venturi formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, a second valve disposed in said induction passage anteriorly of said venturi, intake passages communicating the induction passage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device to provide heated air flow through said nozzles, means responsive to engine temperature for causing said air flow to bypass said device as engine temperature increases, and means interconnecting said temperature responsive means and said signal modifier valve whereby said valve will be opened as engine temperature increases.

7. A fuel injection system for an internal combustion engine comprising an air intake passage having a venturi formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, a signal modifier valve disposed in said induction passage anteriorly of said venturi, intake passages communicating the induction passage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device to provide heated air flow through said nozzles, means responsive to engine temperature operatively connected to said device for bypassing air flow therearound as engine temperature increases, means interconnecting said temperature responsive means and said signal modifier valve whereby said valve will be opened as engine temperature increases, and means for interrupting the operative connection between said device and said temperature responsive means.

8. A fuel injection system for an internal combustion engine comprising a cylinder head, a plurality of intake passages mounted on said cylinder head and adapted to respectively communicate with the intake for each cylinder of the engine, an air manifold communicating with said intake passages, an induction passage adapted to supply air to said manifold, a venturi in said induction passage, a throttle valve disposed in said induction passage posteriorly cfsaid venturi, an exhaust passage formed in said cylinder'head, an air flow controlling mechanism supported on said cylinder head and projecting within said exhaust passage, a nozzle disposedin each intake passage, first conduit means for supplying fuel to each nozzle, passage means for communicating air to said nozzle for mixture with said fuel prior to injection into said intake passage, said air flow controlling mechanism including a closed casing member projecting within said exhaust passage, second conduit means communicating said induction passage with said air flow mechanism for supplying air thereto, said nozzle air passage connected with said mechanism, valve means within said mechanism for controlling the flow of air there-through, temperature responsive means disposed in the casing member and exposed to the heat within said exhaust passage, and means connecting said temperature responsive member and said valve means for controlling the fiow through said heater mechanism in accordance with engine temperature.

9. Afuel injection system for an internal combustion enginge comprising a cylinder head, a plurality of intake passages mounted on said cylinder head and adapted to respectively communicate with the intake for each cylinder of the engine, an air manifold communicating with said intake passages, an induction passage adapted to supply air to said manifold, a venturi in said induction passage, a throttle valve disposed in said induction pass-age postericrly of said venturi, an exhaust passage formed in said cylinder head, an air flow controlling mechanism supported on said cylinder head and projecting within said exhaust passage, a nozzle disposed in each intake passage, first conduit means for supplying fuel to each nozzle, passage means for communicating air to said nozzle for mixture with said fuel prior to injection into said intake passage, said air flow controlling mechanism including a closed casing member projecting Within said exhaust passage, second conduit means. communicating said induction passage with said air flow mechanism for supplying air "thereto, said nozzle air passage connected with said mechanism, valve means Within said mechanism for controlling the flow of air therethrough, temperature responsive means disposed in the casing member and exposed to the heat within said exhaust passage, means connecting said temperature responsive member and said valve means for controlling the flow through said heater mechanism in accordance with engine temperature, and means for interrupting the operative connection between said mechanism and said temperature responsive means.

10. ,A fuel injection system for an internal combustion engine comprising acylinder head, a plurality of intake passages mounted on said cylinder head and adapted to respectively communicate with the intake for each cylinder. of the engine, an air manifold communicating with said intake passages, an induction passage adapted to supply air to said manifold, a venturi in said induction passage, a throttle valve disposed in said induction passage posteriorly of said venturi, a second valve in saidinduction passage anteriorly of said venturi, an exhaust pas sage formed in said'cylinder head, an air flow control ling mechanism supported on said cylinder head and pro-- jecting within said exhaust passage, a nozzle disposed in each intake passage, first conduit means for supplying fuel to each nozzle, passage means for communicating air to said nozzle for mixture with said fuel prior to injection into said intake passage, said air flow controlling mechanism including a closed casing member projecting within said exhaust passage, second conduit means communicating said induction passage with said air fiow' mechanism for supplying air thereto, said nozzle air passage connected with said mechanism, valve means within said mechanism for controlling the flow of air thereflow through said heater mechanism in accordance with teriorly of saidv venturi, a second valve in said induction passage anteriorly of said venturi, an exhaust passage formed in' said cylinder head, an air flow controlling mechanism supported on said cylinder head and projecting within said exhaust passage, a nozzle disposed in each intake passage, first conduit means forsupplying fuel to each nozzle, passage means for communicating air to said nozzle for mixture with said fuelprior to injection into said intake passage, said air flow controlling mechanism including a closed casing member projecting within said exhaust passage, second conduit means communicating said induction passage with said air flow mechanism for supplying air thereto, said nozzle air passage connected with said mechanism, valve means within said mechanism for controlling the flow of air therethrough, temperature responsive means disposed in the casing member and exposed to the heat within said exhaust passage, first means connecting said second valve and said temperature responsive member for opening said valve as engine temperature increases, and second means for connecting said valve means with said first means for controlling the flow through said heater mechanism in accordance with engine temperature.

12. A fuel injection system as defined in claim 11 in which said second connecting means includes a device for interrupting the connection between the first connecting means and the valve means and for locking the latter means in a position to bypass air flow around the mechanism casing portion projecting Within the exhaust passage.

13. A fuel injection system for an internal combustion engine as defined in claim 11 in which said air flow mechanism comprises a first tubular portion, a longitudinally extending wall in said first tubular portion dividing said portion into inflow and outflow chambers, said thermostatic element being disposed in the lower portion of said tubular portion whereby air flowing through said cham bers will flow around said thermostatic element, a second tubular section associated With said first section, said nozzle air passage and said second conduit means communicating with said second section, said valve means being adapted when in a first position to cause the air to flow through said mechanism to directly connect said air passage and second conduit means, said valve being movable by said thermostatic element to a second position in which the air flowing through said mechanism is diverted through said first tube portion to be heated by said exhaust passage prior to flowing to. the nozzle air passage.

14. A fuel injection system for an internal combustion engine comprising an air intake passage having a venturi formed therein, a throttle valve disposed in said intake passage posteriorly of said venturi, intake passages communicating the induction passage with the individual cylinders of the engine, a nozzle disposed in each intake passage, conduit means supplying fuel to said nozzle, passage means for supplying air from said induction passage to said nozzle for mixture with the fuel prior to its injection into the intake passage, said passage means including a device to provide heated air flow through said nozzles, and means responsive to engine temperature disposed in said, device for bypassing said device as engine temperature increases, and a conduit communicating at one end with the intake passage posteriorly of said throttle and 9 at the other end with said device to insure a continuous flow of air over said temperature responsive means.

15. A fuel injection system for an internal combustion engine as defined in claim 11 in which said air flow mechanism comprises a first tubular portion, a longitudinally extending wall in said first tubular portion dividing saidvportion into inflow and outflow chambers, said thermostatic element being disposed in the lower portion of said tubular portion whereby air flowing through said 10 communicating with said second section, said valve means including a first element permitting direct air flow from said second conduit means to said nozzle air passage and a second element for blocking air flow from said chambers to said nozzle air passage, said elements being movable in unison by said thermostatic element to a position in which said first element blocks direct air flow between said second conduit means and the nozzle air passage and said second element permits air to flow from said chambers will flow around said thermostatic element, a 10 chambers to said nozzle air passage.

second tubular section associated with said first section, said nozzle air passage and said second conduit means No references cited. 

